1. Field of the Invention
The invention is related to cooktops having flat glass ceramic surfaces.
2. Background Art
Cooktops having flat glass ceramic plates for the cooking surface on which pots, pans or other cooking utensils are placed to be heated are well known in the art. The flat glass ceramic surface has many advantages. They provide a unitary surface which is aesthetically pleasing to the eye. Further, the ceramic glass cooktop greatly enhances the ease with which the cooktop may be cleaned and they do not require a precise positioning of the pot or pan to be heated. On the other hand, the glass ceramic cooktops have the disadvantage that they are more fragile than metal cooktop surfaces and are more subject to mechanical and thermal stress than cooktops made of metal.
Various means have been used to mount glass ceramic cooktops in a cutout or receptacle provided in a kitchen countertop. For example, Steiner et al in U.S. Pat. No. 5,844,206 teaches the use of a plastic frame injection molded about the periphery of the glass ceramic plate. This plastic frame supports the cooktop in the countertop recess. The frame includes an outwardly extending flange which engages the countertop about the edges of the recess. Alternatively, Stedron et al in U.S. Pat. No. 6,207,933 teaches the use of a metal frame circumscribing the periphery of the glass ceramic plate. Stedron et al""s frame also includes an outwardly extending flange outside the perimeter of the glass ceramic plate. A reactive adhesive foam is used to bond the glass ceramic plate to the metal frame.
Alternatively, Stedron et al in U.S. Pat. No. 6,043,462 discloses a metal frame attached to the back side of the glass ceramic plate and has an outwardly extending flange underlying the glass ceramic plate adjacent to its periphery.
The invention is a multi-piece frame attached to the bottom surface of the glass ceramic plate which is more flexible and induces less stress on the glass ceramic plate.
A cooktop receivable in a cutout of a countertop having a glass ceramic plate sized to completely cover the cutout. Front, rear and side rails are independently attached to the bottom surface of the glass ceramic plate. The front, rear, and side rails have at least a U-shaped portion and an outwardly extending flange extending to a region overlapping the edges of the cutout. A plurality of heating elements are supported against the bottom surface of the glass ceramic plate from the front, rear and side rails plus a control box containing the electronic controls providing electrical power to the heating elements. The back side of the cooktop is enclosed by a three-piece rough in-box consisting of a U-shaped primary cover connected to the opposing rails and two side covers enclosing the open ends of the primary cover, the side covers being attached to the side rails.
One object of the invention is a cooktop having a glass ceramic plate capable of sustaining without damage the U.L. drop test.
Another object of the invention is a cooktop having front, rear and side rails independently attached to the glass ceramic plate. The ends of the front, rear and side rails are not connected at the corners to reduce the stress in the glass ceramic plate.
Another object of the invention is to provide the front, rear and side rails with outwardly extending flanges which overlap the edges of the cutout of the countertop. The outwardly extending flanges being maintained within the periphery of the glass ceramic plate.
Still another object is to provide detents on the outwardly extending flanges extending away from the glass ceramic plate to minimize the thermal contact area between the outwardly extending flanges and the countertop.
Another object is to provide a recess in the outwardly extending flanges between the detents to reduce heat flow to the countertop.
Another object of the invention is to provide a slot between each detent and the U-shaped portion of the front rear and side rails to minimize heat flow to the countertop.
Still another object of the invention is to attach insulating pads to the outwardly extending flanges on the side opposite the glass ceramic plate to minimize heat flow to the countertop.
Still another object of the invention is to provide at least one crossbar connected between the front and rear rails to help support at least one heating element.
Another object is to attach springs to the crossbar resiliently biasing the heating element against the bottom surface of the glass ceramic plate.
Another object is to reduce the thermal contact between the crossbar and the front and rear rails to which it is attached.
Yet another object is to provide thermal insulating pads between the crossbar and the rails to which it is attached.
A final object of the invention is to provide a three-piece rough-in-box to minimize stresses on the glass ceramic plate.